A magnetic heat pump system is known in the art, for example, as disclosed in Japanese Patent No. 4387892, as a heat pump system of an air conditioning apparatus for a vehicle, for example, an air conditioning apparatus for a motor vehicle or a railroad vehicle. In the magnetic heat pump system, a certain kind of magnetic material (which is referred to as “magnetic working material” in the above Japanese Patent, but referred to as “magnetocaloric effect material” in this disclosure) is used. When magnetic field is applied to the magnetocaloric effect material, heat is generated in the magnetocaloric effect material, while when the magnetic field is removed, temperature thereof is decreased (this phenomenon is called as “magnetocaloric effect”).
When compared with a gas heat pump system, since chlorofluorocarbon or alternatives for chlorofluorocarbon is not used for the magnetic heat pump system, it is environmentally friendly. In addition, since a compression stroke and an expansion stroke, which are necessary for the gas heat pump system using a compressor, are not required for the magnetic heat pump system, energy efficiency is high. Components, which are necessary for the magnetic heat pump system, are (i) a pump for moving heat transport medium so that it passes through magnetocaloric effect material in order to carry out heat exchange therewith and (ii) a magnetic field changing device for changing magnetic field to be applied to the magnetocaloric effect material.
In a conventional magnetic heat pump system or in a conventional air conditioning apparatus having the magnetic heat pump system, water or anti-freeze liquid (LLC: a long life coolant) is used as heat transport medium, which passes through the magnetocaloric effect material so that heat exchange is carried out between the heat transport medium and the magnetocaloric effect material. The water or the anti-freeze liquid is generally used as heat transporting medium but heat-exchange performance is not high.
Therefore, in a case that a cooling performance will be increased for the magnetic heat pump system, in which the water or the anti-freeze liquid is used, it is necessary to make the magnetic heat pump system larger in its size. It is, then, a disadvantage that weight of the magnetic heat pump system will be increased.